Time for Potato wisdom...
My perspective on the whole "is it OP argument" centers around if the card is considered an "auto include". Examples of this would be Demo back in the day. It was dang near impossible to play in a tournament without 80%+ imperial lists containing demo. Did that mean it was unbeatable? No. But should a card be considered so good that its an auto include? Another example is Major Ryhmer. I remember I looked up the stats for Warlord website and it was something absurd that imperial lists with bombers had an roughly 75% probability that they would also have Major Rhymer. Again, I don't think lists with Major Rhymer were unbeatable but the card definitely fell in the "auto include" category.
That is bad and I 100% approved of the nerf bat FFG brought down on those cards... in fact I think it took them way to long to do it.
Now to the BT Avenger... is it unbeatable? No. But is it an auto include when fielding an ISD? Debatable as the previous posts have indicated. But if its debatable than there may be an argument to be made that maybe something is out of wack. I think its too early for for the nerf bat but hopefully its be watched by the people in high places.